Patent Document 1 describes a chelate-introduced macromolecule obtained by allowing a maleic anhydride-graft modified polymer to react with a chelate ligand of a polyphosphoric acid having a hydroxyl group or an amino group, an amino polycarboxylic acid or 1,3-diketone to further introduce these functional groups into the maleic anhydride group. Patent Document 1 also describes that a rubber such as EPR, BR and IR may be used as a polymer to be graft modified, and the chelate structure can reliably bind with a thioester bond and the like. However, the chelate structure is formed through the maleic anhydride grafted into a polymer.